no framing concrete slab bathroom floor needs to be repaired in one spot

barrr

I have to install a ceramic tile floor in a bathroom. But the bathroom floor is un even whoever installed the tiolet put to much concrete around it so the floor is uneven. So when i took up the vinyl tile that was on top and started to chip away at the excess concrete the tile floor under the vinyl floor (original floor) broke and fell and thats when i realized that the floor is not framed. So my question is how do i repair that section of the floor without having to tear the whole floor out

joecaption

Before you can doing any tiling you have to know 100% what's under that floor.
If this floor over a slab, foundation?
Post a picture of what you have.
I'm thinking it could be an old style mud job, which is morter pored over a subfloor. Only guessing.